The Enterprise scans an anti-time eruption with an inverse tachyon pulse

Anti-time was a concept in temporal mechanics, conceived in the 24th century, positing the existence of a phenomenon which has a relationship to time analogous to the relationship that antimatter has to normal matter. Consequently, if time and anti-time were to collide, they would annihilate one another, creating a rupture in space.

Such a rupture was observed in an alternate timeline, caused by the convergence of three tachyon pulses initiated at the same spatial coordinates in three different time periods, which ruptured the subspace barrier creating an anti-time reaction. Due to anti-time's opposite nature relative to normal time, the rupture traveled backwards in time, growing larger as it did so. The rupture eventually grew to encompass the entire Alpha Quadrant by approximately 3.5 billion years previous, disrupting the initial formation of life on Earth. This timeline was later negated, however, when CaptainJean-Luc Picard, with assistance from Q, was able to prevent the formation of the rupture in the first place. (TNG: "All Good Things...")